dev-arm,misc: Added missing override to scmi_platform functions

dev-arm,misc: Added missing override to scmi_platform functions

The missing overrides on the "raiseInterrupt" and "clearInterrupt"
resulted in compilation failures when using Clang.

Change-Id: Ic77e8587cd622f8f0cb819c3230893a1b169a2a2
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/37355
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>